Air intake device for engine

ABSTRACT

An air intake device for an engine is provided that includes a throttle body ( 1 ), a throttle valve ( 5 ) that has a valve shaft ( 5   a ) rotatably supported on the throttle body ( 1 ), a throttle drum ( 8 ) connected to one end of the throttle valve ( 5 ), a throttle sensor ( 51 ) connected to the other end of the valve shaft ( 5   a ), a bypass ( 20 ) bypassing the throttle valve ( 5 ), and a bypass valve ( 25 ) that opens and closes the bypass ( 20 ), a bearing boss ( 3 ) supporting one end part, on the throttle drum ( 8 ) side, of the valve shaft ( 5   a ) being integrally and projecting provided on one side face of the throttle body ( 1 ), wherein the bypass ( 20 ) is formed so as to surround the bearing boss ( 3 ). This enables the air intake device for an engine to be made compact in spite of the bypass being present.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Stage entry of International ApplicationNo. PCT/JP2006/316093, filed Aug. 16, 2006, the entire specificationclaims and drawings of which are incorporated herewith by reference.

TECHNICAL FIELD

The present invention relates to an improvement of an air intake devicefor an engine, the air intake device including a throttle body having anair intake path, a butterfly throttle valve that has a valve shaftrotatably supported on the throttle body and that opens and closes theair intake path, a throttle drum connected to one end of the valve shaftso as to open and close the throttle valve, a throttle sensor that isconnected to the other end of the valve shaft and that detects a degreeof opening of the throttle valve, a bypass connected to the air intakepath while bypassing the throttle valve, and a bypass valve that opensand closes the bypass, a bearing boss supporting one end part, on thethrottle drum side, of the valve shaft being integrally and projectinglyprovided on one side wall of the throttle body.

BACKGROUND ART

Such an air intake device for an engine is already known, as disclosedin Patent Publication 1.

[Patent Publication 1] Japanese Patent Application Laid-open No.2003-74444

DISCLOSURE OF INVENTION Problems To Be Solved By the Invention

In the conventional air intake device for an engine, since a controlblock is joined to a side of the throttle body opposite to the throttledrum, and a throttle sensor, an electronic control unit, and a bypassvalve are concentrated on the control block, the control block has largedimensions, thus resulting in an increase in the overall dimensions ofthe device.

The present invention has been accomplished in the light of suchcircumstances, and it is an object thereof to provide an air intakedevice for an engine of the above type that can be made compact in spiteof the bypass being present.

Means for Solving the Problems

In order to attain the above object, according to a first aspect of thepresent invention, there is provided an air intake device for an engine,comprising a throttle body having an air intake path, a butterflythrottle valve that has a valve shaft rotatably supported on thethrottle body and that opens and closes the air intake path, a throttledrum connected to one end of the valve shaft so as to open and close thethrottle valve, a throttle sensor that is connected to the other end ofthe valve shaft and that detects a degree of opening of the throttlevalve, a bypass connected to the air intake path while bypassing thethrottle valve, and a bypass valve that opens and closes the bypass, abearing boss supporting one end part, on the throttle drum side, of thevalve shaft being integrally and projectingly provided on one side wallof the throttle body, characterized in that the bypass is formed so asto surround the bearing boss and surround a return spring of thethrottle drum, the return spring being mounted so as to surround thebearing boss.

According to a second aspect of the present invention, in addition tothe first aspect, a bypass valve holder is joined to one side face ofthe throttle body, the bypass valve holder holding the bypass valve andalso surrounding the bearing boss, and a groove-shaped recess is formedin at least one of opposing faces of the throttle body and the bypassvalve holder, the groove-shaped recess forming at least part of thebypass.

According to a third aspect of the present invention, in addition to thesecond aspect, center lines of an inlet port and an outlet port of thebypass, which open in the air intake path, are made parallel to the axisof the valve shaft.

According to a fourth aspect of the present invention, in addition tothe second aspect, groove-shaped recesses are formed in both opposingfaces of the throttle body and the bypass valve holder, thegroove-shaped recesses forming at least part of the bypass, andlabyrinth walls are provided in the recesses, the labyrinth wallstraversing the corresponding recesses at different positions from eachother.

According to a fifth aspect of the present invention, in addition to thesecond aspect, a full closure regulation part is provided integrallywith the throttle body, the full closure regulation part running throughthe bypass valve holder and projecting on the throttle drum side, and afully closed position of the throttle valve is regulated by the fullclosure regulation part receiving the throttle drum.

According to a sixth aspect of the present invention, in addition to thesecond aspect, a throttle wire is connected to the throttle drum, thethrottle wire pivoting the throttle drum, and a support part forsupporting a guide tube slidably covering the throttle wire is formed onthe bypass valve holder.

According to a seventh aspect of the present invention, in addition tothe second or sixth aspect, a tubular wall covering an outer peripheryof the throttle drum is formed integrally with the bypass valve holder,and a cover for closing an open face of the tubular wall is mounted onthe tubular wall.

Effects of the Invention

In accordance with the first aspect of the present invention, since thespace around the outer periphery of the bearing boss on the throttledrum side, which is conventionally considered to be dead space, isutilized effectively for formation of the bypass, it is possible to makethe overall air intake device compact while preventing the dimensions ofthe area around the throttle sensor on the side opposite to the throttledrum from increasing.

In accordance with the second aspect of the present invention, even ifthe shape of the bypass is complicated, at least one part thereof can beformed easily at the same time as molding the throttle body or thebypass valve holder.

In accordance with the third aspect of the present invention, it becomespossible to machine the throttle body so as to coaxially form the inletport and the outlet port and the shaft hole of the bearing boss, therebycontributing to a reduction in the number of machining steps.

In accordance with the fourth aspect of the present invention, it ispossible to simply form a labyrinth in the bypass, and even when theengine blows back and the blown back gas flows backward in the bypass,carbon contained in the gas can be trapped in the labyrinth and thusprevented from entering the bypass valve.

In accordance with the fifth aspect of the present invention, even ifthe bypass valve holder is displaced to some degree, the fully closedposition of the throttle valve can always be obtained accurately byabutment of the throttle drum against the full closure regulation partthat is integral with the throttle body, regardless of the displacement.

In accordance with the sixth aspect of the present invention, the bypassvalve holder also functions as a support member for supporting the endpart of the guide tube of the throttle wire, thus reducing the number ofcomponents and the number of assembly steps.

In accordance with the seventh aspect of the present invention, thethrottle drum and the area around the shaft end of the valve shaft arecovered in a substantially hermetically sealed manner by the tubularwall of the bypass valve holder and the cover, thus providing protectionagainst dust and water therefor and, moreover, since the tubular wall isformed on the bypass valve holder, it is possible to suppress anyincrease in the number of components and simplify the structure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional side view of an air intake device for an engine,related to the present invention (first embodiment).

FIG. 2 is a sectional view along line 2-2 in FIG. 1 (first embodiment).

FIG. 3 is a sectional view along line 3-3 in FIG. 1 (first embodiment).

FIG. 4 is a sectional view along line 4-4 in FIG. 1 (first embodiment).

FIG. 5 is a sectional view along line 5-5 in FIG. 4 (first embodiment).

FIG. 6 is a sectional view along line 6-6 in FIG. 5 (first embodiment).

FIG. 7 is a sectional view along line 7-7 in FIG. 3 (first embodiment).

FIG. 8 is a view from arrow 8 in FIG. 2 (first embodiment).

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS

-   1 Throttle body-   2 Air intake path-   3 Bearing boss (first bearing boss)-   5 Throttle valve-   5 a Valve shaft-   8 Throttle drum-   10 Bypass valve holder-   13 Recess-   14 Recess-   18 Inlet port-   19 Outlet port-   20 Bypass-   25 Bypass valve-   31 Labyrinth wall-   32 Labyrinth wall-   37 Full closure regulation part-   39 Tubular wall-   40 Support part (support boss)-   41 Throttle wire-   42 Guide tube-   45 Cover-   51 Throttle sensor

BEST MODE FOR CARRYING OUT THE INVENTION

Modes for carrying out the present invention are explained below byreference to a preferred embodiment of the present invention shown inthe attached drawings.

Embodiment 1

First, in FIG. 1 and FIG. 2, the air intake device for an engine of thepresent invention includes a throttle body 1 having a horizontal airintake path 2 communicating with an air intake port (not illustrated) ofthe engine. First and second bearing bosses 3 and 4 are formed in middlesections of opposing side walls of the throttle body 1 so as to projectoutward, a valve shaft 5 a of a butterfly throttle valve 5 for openingand closing the air intake path 2 is rotatably supported by thesebearing bosses 3 and 4, and the bearing bosses 3 and 4 are equipped withseals 6 and 7 respectively, which make intimate contact with the outerperipheral face of the valve shaft 5 a. A throttle drum 8 is fixedlyattached to one end portion of the valve shaft 5 a projecting outwardfrom the first bearing boss 3. Furthermore, a fuel injection valve 9 ismounted on an upper wall of the throttle body 1, the fuel injectionvalve 9 being capable of injecting fuel toward the air intake path 2 onthe downstream side of the throttle valve 5.

As shown in FIG. 3 to FIG. 7, joined by a bolt to a side face of thethrottle body 1 on the throttle drum 8 side is a bypass valve holder 10extending around and fitted onto an outer periphery of the first bearingboss 3 via a seal 11, formed in a face 1 f of the throttle body 1,opposing the bypass valve holder 10, is a groove-shaped first recess 13surrounding the first bearing boss 3, and formed in a side face 10 f ofthe bypass valve holder 10, opposing the throttle body 1, is agroove-shaped second recess 14 that passes above the first bearing boss3 and is superimposed on an upper part of the first recess 13.Furthermore, formed in the bypass valve holder 10 are a verticallyextending cylindrical valve chamber 15 and a pair of metering holes 16and 16′ (see FIG. 1, FIG. 3, and FIG. 6) for providing communicationbetween a vertically middle section of the valve chamber 15 and one endpart of the second recess 14. These metering holes 16 and 16′ arearranged in the peripheral direction with a dividing wall 17 interposedtherebetween.

A lower end part of the valve chamber 15 communicates with the airintake path 2 on the upstream side of the throttle valve 5 via an inletport 18 (see FIG. 1 and FIG. 4) formed from the throttle body 1 to thebypass valve holder 10. Furthermore, the other end part of the firstrecess 13 communicates with the air intake path 2 on the downstream sideof the throttle valve 5 via an outlet port 19 (see FIG. 1, FIG. 3, andFIG. 5) formed from the throttle body 1 to the bypass valve holder 10.In this arrangement, the inlet port 18 and the outlet port 19 aredisposed so that center lines thereof are parallel to the axis of thefirst bearing boss. 3, 4. It is therefore possible to machine thethrottle body 1 so as to coaxially form the inlet port 18, the outletport 19, and a shaft hole of the first bearing boss 3, 4.

The inlet port 18, the valve chamber 15, the metering holes 16 and 16′,the recesses 13 and 14, and the outlet port 19 thereby form a bypass 20connected to the air intake path 2 while surrounding the first bearingboss 3 and bypassing the throttle valve 5. A seal 21 is provided betweenthe opposing faces 1 f and 10 f of the throttle body 1 and the bypassvalve holder 10 so as to surround the recesses 13 and 14, the inlet port18, and the outlet port 19.

As clearly shown in FIG. 4, a piston-shaped bypass valve 25 foradjusting the degree of opening of the metering holes 16 and 16′ from afully closed state to a fully open state is slidably fitted into thevalve chamber 15 from above, and in order to prevent the bypass valve 25from rotating in this arrangement, a key 27 slidably engaging with a keygroove 26 in the side face of the bypass valve 25 is mounted on thebypass valve holder 10. An electric actuator 28 for moving the bypassvalve 25 for opening and closing is fitted into a mounting hole 29formed in the bypass valve holder 10 so as to communicate with the upperend of the valve chamber 15, and is fixedly secured to the bypass valveholder 10. This electric actuator 28 has a downwardly projecting outputshaft 28 a screwed into a screw hole 25 a in a center part of the bypassvalve 25, and rotating the output shaft 28 a forward and backwardenables the bypass valve 25 to move up and down (open and close). Aplate-shaped seal 30 is provided between a lower end face of theelectric actuator 28 and a base face of the mounting hole 29, the seal30 making intimate contact with an outer peripheral face of the outputshaft 28 a.

As shown in FIG. 1, FIG. 3, FIG. 5, and FIG. 6, a plurality (two in theillustrated example) of labyrinth walls 31 and 32 are formed on thethrottle body 1 and the bypass valve holder 10 in a section where thefirst and second recesses 13 and 14 are superimposed upon each other,the labyrinth walls 31 and 32 being arranged alternately along thedirection of flow of air while traversing the recesses 13 and 14. Inthis arrangement, the first labyrinth wall 31 on the bypass valve holder10 side is provided so as to be connected to the dividing wall 17between the pair of metering holes 16 and 16′.

In FIG. 2 and FIG. 8, a return spring 35, which is a torsion coilspring, urging the throttle drum 8 in a direction that closes thethrottle valve 5 is mounted between the bypass valve holder 10 and thethrottle drum 8 so as to surround the first bearing boss 3. Furthermore,a full closure regulation part 37 running through a through hole 36 ofthe bypass valve holder 10 and projecting toward the throttle drum 8side is formed integrally with the throttle body 1, and a stopper bolt38 adjustably screwed into a forward end part of the full closureregulation part 37 regulates a fully closed position of the throttlevalve 5 by receiving a bent stopper piece 8 a of the throttle drum 8.

Formed integrally with the bypass valve holder 10 is a tubular wall 39surrounding the throttle drum 8 and being integrally equipped with asupport boss 40 on one side, linked to the throttle drum 8 is aconnection terminal 41 a at one end of a throttle wire 41 runningthrough the support boss 40, and linked to a throttle operation membersuch as a throttle grip (not illustrated) is a connection terminal atthe other end of the throttle wire 41. A hollow bolt 43 through whichthe throttle wire 41 runs is adjustably screwed into the support boss40, and an end part of a guide tube 42 slidably covering the throttlewire 41 is supported by a head portion 43 a of the hollow bolt 43.

Pulling the throttle wire 41 by the throttle operation member enablesthe throttle valve 5 to be opened via the throttle drum 8, and releasingthe pulling enables the throttle valve 5 to be closed by the urgingforce of the return spring 35.

A cover 45 for closing an open face of the tubular wall 39 is detachablyretained on the tubular wall 39 by a screw.

Referring again to FIG. 2, a control block 50 covering an end face ofthe second bearing boss 4 is joined to the throttle body 1, and athrottle sensor 51 for detecting a degree of opening of the throttlevalve 5 is formed between the control block 50 and the valve shaft 5 a.Furthermore, provided in the control block 50 is a through hole 52adjacent to the second bearing boss 4, and mounted on the control block50 is a temperature sensor 53 running through the through hole 52 andhaving its forward end part facing the air intake path 2 on the upstreamside of the throttle valve 5. Furthermore, mounted on the control block50 is an electronic control unit 54 that receives detection signals fromthe throttle sensor 51, the temperature sensor 53, etc. and controls theoperation of the electric actuator 28, the fuel injection valve 9, anignition system, etc.

The operation of this embodiment is now explained.

When the engine is running, the electronic control unit 54 supplies tothe electric actuator 28 a current corresponding to an air intaketemperature detected by the temperature sensor 53, thus operating theelectric actuator 25 and thereby controlling the opening and closing ofthe bypass valve 25. When the engine is at a low temperature, that is,the engine is warming up, the bypass valve 25 is pulled up by a largeamount, thus controlling the degree of opening of the metering holes 16and 16′ so that it is large. When the throttle valve 5 is in a fullyclosed state, the amount of fast idle air that is supplied to the enginethrough the bypass 20, that is, in sequence through the inlet port 18,the valve chamber 15, the metering holes 16 and 16′, the first andsecond recesses 13 and 14, and the outlet port 19, is controlled so asto be relatively large by the degree of opening of the metering holes 16and 16′; at the same time an amount of fuel corresponding to the airintake temperature is injected from the fuel injection valve 9 towardthe downstream side of the air intake path 2, and the engine receives asupply of the fast idle air and the fuel, thus maintaining anappropriate fast idling rotational speed so as to accelerate the warmingup.

When the engine temperature increases as warming up progresses, sincethe electric actuator 28 accordingly makes the bypass valve 25 descend,thus decreasing the degree of opening of the metering holes 16 and 16′,the amount of fast idle air supplied to the engine through the bypass 20decreases, and the engine fast idling rotational speed decreases. Whenthe engine temperature reaches a predetermined high temperature, sincethe electric actuator 28 maintains the bypass valve 25 at apredetermined degree of idle opening, the engine can be put stably intoa normal idling state when the throttle valve 5 is fully closed.

Since the bypass 20 is formed so as to surround the first bearing boss3, which supports the end part of the valve shaft 5 a on the throttledrum 8 side, the space around the outer periphery of the first bearingboss 3, which is conventionally considered to be dead space, is utilizedeffectively for formation of the bypass 20, and it is therefore possibleto make the overall air intake device compact while preventing thedimensions of the area around the throttle sensor 51 on the sideopposite to the throttle drum 8 from increasing.

Furthermore, since at least one part of the bypass 20 is formed from thegroove-shaped recesses 13 and 14 formed in opposing faces of thethrottle body 1 and the bypass valve holder 10, which are joined to eachother, even if the shape of the bypass 20 is complicated, at least onepart thereof can be formed easily at the same time as molding thethrottle body 1 and the bypass valve holder 10.

Moreover, since the center lines of the inlet port 18 and outlet port 19of the bypass 20, which open on the air intake path 2, are parallel tothe axis of the valve shaft 5 a, it is possible to machine the throttlebody 1 so as to coaxially form the inlet port 18 and the outlet port 19and the shaft hole of the bearing boss, thereby contributing to areduction in the number of machining steps.

Furthermore, since, in order to form the bypass 20, a plurality oflabyrinth walls 31 and 32 are provided on the groove-shaped recesses 13and 14 formed in the two opposing faces 1 f and 10 f of the throttlebody 1 and the bypass valve holder 10, the labyrinth walls 31 and 32being arranged alternately along the direction of flow of air whiletraversing the recesses 13 and 14, it is possible to simply form alabyrinth in the bypass 20, and even when the engine blows back and theblown back gas flows backward in the bypass 20, carbon contained in thegas can be trapped in the labyrinth and thus prevented from entering thebypass valve 25.

Furthermore, since the full closure regulation part 37 running throughthe bypass valve holder 10 and projecting toward the throttle drum 8side is formed integrally with the throttle body 1, and the fully closedposition of the throttle valve 5 is regulated by means of the stopperbolt 38, which is screwed into the full closure regulation part 37,receiving the stopper piece 8 a of the throttle drum 8, even if thebypass valve holder 10 is displaced relative to the throttle body 1 tosome degree, the fully closed position of the throttle valve 5 canalways be reproduced accurately regardless of the displacement.

Moreover, since the tubular wall 39 covering the outer periphery of thethrottle drum 8 is formed integrally with the bypass valve holder 10,and the cover 45 is mounted on the open end of the tubular wall 39 so asto block it, the throttle drum 8 and the area around the shaft end ofthe valve shaft are covered in a substantially hermetically sealedmanner by the tubular wall 39 of the bypass valve holder 10 and thecover 45, thus providing protection against dust and water therefor and,moreover, since the tubular wall 39 is formed on the bypass valve holder10, it is possible to suppress any increase in the number of componentsand simplify the structure.

Furthermore, since the support boss 40 supporting the guide tube 42 ofthe throttle wire 41 is formed integrally with the tubular wall 39, thetubular wall 39, that is, the bypass valve holder 10, functions also asa support member for supporting the end part of the guide tube 42 of thethrottle wire 41, thus reducing the number of components and the numberof assembly steps.

Furthermore, since the metering holes 16 and 16′, whose degree ofopening is controlled by the bypass valve 25, are formed as a pair ofseparate metering holes 16 and 16′ arranged in the peripheral directionof the valve chamber 15 with the dividing wall 17 interposedtherebetween, the total opening area of the two metering holes 16 and16′ is large; even if the bypass valve 25 is drawn toward the meteringholes 16 and 16′ side by air intake negative pressure on the downstreamside of the bypass 20 acting on the outer peripheral face of the bypassvalve 25 through the two metering holes 16 and 16′, since the outerperipheral face of the bypass valve 25 is supported by the dividing wall17, it is possible to prevent effectively the outer peripheral face ofthe bypass valve 25 from being forced out toward the metering holes 16and 16′ side, thus guaranteeing a smooth opening and closing (up anddown) movement of the bypass valve 25. It is therefore possible tosupply a large volume of fast idle air by setting the total opening areaof the two metering holes 16 and 16′ sufficiently large.

An embodiment of the present invention is explained above, but thepresent invention is not limited thereto and may be modified in avariety of ways as long as the modifications do not depart from thespirit and scope of the present invention. For example, the presentinvention may be applied to a downdraft type throttle body having itsair intake path standing vertically.

1. An air intake device for an engine, comprising: a throttle bodyhaving an air intake path; a butterfly throttle valve that has a valveshaft rotatably supported on the throttle body and that opens and closesthe air intake path; a throttle drum connected to one end of the valveshaft so as to open and close the throttle valve; a throttle sensor thatis connected to another end of the valve shaft and that detects a degreeof opening of the throttle valve; a bypass connected to the air intakepath and bypassing the throttle valve; a bypass valve that opens andcloses the bypass; and a bearing boss, supporting an end part, on thethrottle drum side, of the valve shaft being integrally and projectinglyprovided on one side wall of the throttle body, wherein the bypass isformed so as to surround the bearing boss and surround a return springof the throttle drum, the return spring being mounted so as to surroundthe bearing boss.
 2. The air intake device for an engine according toclaim 1, wherein a bypass valve holder is joined to one side face of thethrottle body, the bypass valve holder holding the bypass valve andsurrounding the bearing boss, and a groove-shaped recess is formed in atleast one of opposing faces of the throttle body and the bypass valveholder, the groove-shaped recess forming at least part of the bypass. 3.The air intake device for an engine according to claim 2, wherein centerlines of an inlet port and an outlet port of the bypass, which open inthe air intake path, are made parallel to the axis of the valve shaft.4. The air intake device for an engine according to claim 2, whereingroove-shaped recesses are formed in both opposing faces of the throttlebody and the bypass valve holder, the groove-shaped recesses forming atleast part of the bypass, and labyrinth walls are provided in therecesses, the labyrinth walls traversing the corresponding recesses atdifferent positions from each other.
 5. The air intake device for anengine according to claim 2, wherein a full closure regulation part isprovided integrally with the throttle body, the full closure regulationpart running through the bypass valve holder and projecting on thethrottle drum side, and a fully closed position of the throttle valve isregulated by the full closure regulation part receiving the throttledrum.
 6. The air intake device for an engine according to claim 2,wherein a throttle wire is connected to the throttle drum, the throttlewire pivoting the throttle drum, and a support part for supporting aguide tube slidably covering the throttle wire is formed on the bypassvalve holder.
 7. The air intake device for an engine according to claim2 or 6, wherein a tubular wall covering an outer periphery of thethrottle drum is formed integrally with the bypass valve holder, and acover for closing an open face of the tubular wall is mounted on thetubular wall.